1. Field of the Invention
The present invention relates to process control methods, and particularly to a reduced complexity auto-tuning process controller system and method that uses a reduced number of constants for auto-tuning.
2. Description of the Related Art
In today's industrial world, Proportional Integral (PI) controllers remain by far, the most commonly used classical feedback controllers in the industry, especially for chemical process with slow dynamics. A PI controller, or for that matter, a P-Only controller, calculates the deviation error between a measured process variable and the desired set-point of the variable. This error is then sought to be minimized by properly tuning the gains of the controller.
A typical three-term controller (e.g., a PID controller) involves tuning of three gains, namely the proportional, the integral and the derivative values, denoted by KP, KI, and KD. In process control, usually, the first two terms, the KP, KI are sufficient, and hence, are used most commonly. These gains are usually interpreted in terms of time-based response. The gain KP, depends on the current value of error, while the gain KI, depends on the accumulation of past errors. The weighted sum of these actions is used to adjust the actuator in order to minimize the deviation error. The basic equation for the PI controller is therefore given by:
                              Gc          ⁡                      (            s            )                          =                              K            p                    ⁢                      {                          1              +                              1                                                      K                    i                                    ⁢                  s                                                      }                                              (        1        )            
The gains KP and KI are the proportional and integral gains respectively, and are positive parameters. In order to tune the gains, a control engineer must have knowledge of the process or system under consideration. Hence, the control engineer needs to know the characteristics of the process. Even in the absence of knowledge of the underlying process, a PI controller is often thought of as the best controller.
In industrial practice, real-time control imposes a time constraint on the performance of the controller. This means that since control decisions are taken in real-time, it is of high importance that high computation machines are available to sample data, acquire data, compute control decisions based on the acquired data, and filially take a decision, all within a small sampling time rate. Sampling time should be small enough to make sure that system dynamics are not missed in-between samples. For the controller to be able to compute all of this in limited time, it needs to harbor computation power. Computation complexity is therefore of tantamount importance. Hence, for the commonly used PI controller, the aim is to reduce the computation complexity required to tune the gains KP and KI.
Thus, a reduced complexity auto-tuning process controller system and method solving the aforementioned problems is desired.